1. Field of the Invention
The present invention relates to an organic anti-reflective coating (“ARC”) material which allows the stable formation of ultrafine patterns suitable for 64 M, 256 M, 1 G, 4 G and 16 G DRAM semiconductor devices. More particularly, the present invention relates to an organic anti-reflective coating material that contains a chromophore with high absorbance at the wavelengths useful for submicrolithography. A layer of said anti-reflection material can prevent back reflection of light from lower layers or a surface of the semiconductor ship, as well as eliminate the standing waves in the photoresist layer, during a submicrolithographic process using a 193 nm ArF laser light sources. Also, the present invention is concerned with an anti-reflective coating composition comprising such a material, an anti-reflective coating therefrom and a preparation method thereof
2. Description of the Prior Art
During a submicrolithographic process, one of the most important processes for fabricating highly integrated semiconductor devices, there inevitably occur standing waves and reflective notching of the waves due to the optical properties of lower layers coated on the wafer and to changes in the thickness of the photosensitive film applied thereon. In addition, the submicrolithographic process generally suffers from a problem of the CD (critical dimension) being altered by the diffracted light and reflected light from the lower layers.
To overcome these problems, it has been proposed to introduce a film, called an anti-reflective coating, between the substrate and the photosensitive film to prevent light reflection from the lower layer. Largely, anti-reflective coatings are classified into “organic” and “inorganic” by the materials used and into “absorbing” and “interfering” by the operation mechanisms.
An inorganic anti-reflective coating is used mainly in the process of ultrafine-pattern formation using i-line radiation with a wavelength of 365 nm. TiN and amorphous carbon have been widely used in light-absorbing coatings, and SiON has been used in light-interfering coatings. The SiON anti-reflective coatings are also adopted for submicrolithographic processes that use KrF light sources.
Recently, extensive and intensive research has been and continues to be directed to the application of organic anti-reflective coatings for such submicrolithography. In view of the present development status, organic anti-reflective coatings, if they are to be useful, must satisfy the following fundamental requirements:
First, during the pattern formation process, the photoresist must not be peeled from the substrate by dissolving in the solvent used in the organic anti-reflective coating. For this reason, the organic anti-reflective coating needs to be designed to form a cross-linked structure, and must not produce chemicals as a by-product.
Second, acid or amine compounds must not migrate in or out of the anti-reflective coating. This is because there is a tendency for undercutting at the lower side of the pattern if an acid migrates, and for footing if a base such as an amine migrates.
Third, the anti-reflective coating must have a faster etching speed compared to the photoresist layer so that the etching process can be performed efficiently by utilizing the photoresist layer as a mask.
Finally, the organic anti-reflective coatings should be as thin as possible while playing an excellent role in preventing light reflection.
As various as anti-reflective coatings are, those which are satisfactorily applicable for submicrolithographic processes using ArF light have thus far not been found. As for inorganic anti-reflective coatings, there have been reported no materials which can control interference at the ArF wavelength, that is, 193 nm. In contrast, active research has been undertaken to develop organic materials into superb anti-reflective coatings. In fact, in most cases of submicrolithography, the coating of photosensitive layers is necessarily followed by organic anti-reflective coatings that prevent the standing waves and reflective notching occurring upon light exposure, and that eliminate the influence of the back diffraction and reflection of light from lower layers. Accordingly, the development of such an anti-reflective coating material showing high absorption properties against specific wavelengths is one of the hottest and most urgent issues in the art.